Investigators have not figured out how the victims are linked or if they knew the man who shot them. So far, all they have is a sketch of a suspect and a possible getaway vehicle, said Cherokee County Sheriff Bill Blanton.
"There's no evidence there is a hit list," Blanton said. "There's no evidence he knows the victims. There's no evidence the victims are connected."
But plenty of evidence links the killings, said Blanton, who would not provide details.
"Yes, we have a serial killer," he said at a news conference.
The latest victims were found in their family's small furniture and appliance shop in the small town of Gaffney, South Carolina, around closing time Thursday. Stephen Tyler, 45, was killed, and his 15-year-old daughter was shot and seriously injured. Tyler's wife, his older daughter and an employee found them, County Coroner Dennis Fowler said.
The latest killing happened one day and about 7 miles from where family members found the bodies of 83-year-old Hazel Linder and her 50-year-old daughter, Gena Linder Parker, bound and shot in Linder's home. Blanton would not say if Tyler and his daughter were also bound.
The killing spree began last Saturday about 10 miles from Tyler's shop. Peach farmer Kline Cash, 63, was found shot in his living room. Investigators said he appeared to have been robbed, but they haven't determined if anything was taken in the latest killings.
The shootings have prompted fear in Cherokee County, 50 miles south of Charlotte, North Carolina, and home to about 54,000 people. The county had just six homicides in all of 2008, and that was double the number reported the year before.
Residents have "their guard up and their gun handy," said Sen. Harvey Peeler, a Republican who represents the area in the state legislature.
By Associated Press Writer Mitch Weiss; AP Writers Jim Davenport and Jeffrey Collins contributed to this report from Columbia